The present invention relates to a disc drive microactuator, and more particularly to a magnetic microactuator utilizing a vertical magnetic circuit contained on a substrate and a flex circuit to provide microactuation force.
The density of concentric data tracks on magnetic discs continues to increase (that is, the size of data tracks and radial spacing between data tracks are decreasing), requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor, to radially position a head on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or microactuator, is necessary to accommodate the more densely spaced tracks.
One promising approach for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional lower resolution actuator motor, thereby effecting head positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning. One design involves inserting a silicon-based thin film structure between the suspension and the slider in a disc drive assembly. A major technical challenge in implementing such a microactuator is to provide sufficiently large actuation force to overcome spring bias forces to drive the head at a speed high enough to accommodate the required bandwidth. Such a design must be realized in a relatively small wafer area, to keep costs reasonable and to allow easy integration into the disc drive design.
Therefore, there is a need in the art for a microactuator design providing large actuation force with reasonable power consumption and within a reasonable wafer area to microposition a transducing head at a speed that accommodates the high bandwidth required by high performance disc drives.
The present invention is a dual-stage actuation assembly for a disc drive having a recording disc rotatable about an axis and a slider supporting a transducing head for transducing data with the disc. The dual-stage actuation assembly includes a movable actuator arm controlled by an actuator motor. A suspension assembly is supported by the actuator arm, and includes a flexure. A microactuator is also provided, including a stator attached to the flexure and a rotor supporting the slider, the rotor being movable with respect to the stator in a first horizontal plane generally parallel to a surface of the disc A magnetic circuit is arranged vertically in a plurality of planes substantially parallel to the first horizontal plane to move the microactuator rotor in the first horizontal plane generally parallel to the surface of the disc in response to a current provided to the magnetic circuit. In an exemplary embodiment, the magnetic circuit includes a bottom ferromagnetic keeper, a plurality of magnets, a patterned conductive coil and a top ferromagnetic keeper, vertically arranged in different horizontal planes. The magnets are operable to move laterally and thereby cause movement of the microactuator rotor in the first horizontal plane generally parallel to the surface of the disc in response to circulation of a current through the patterned conductive coil.
Another aspect of the present invention is a method of forming a microactuator in a disc drive having a recording disc rotatable about an axis, a slider supporting a transducing head for transducing data with the disc, and an actuation system supporting the slider to coarsely position the transducing head adjacent a selected radial track of the disc. A microactuator substrate is formed with a plurality of outer preloading bars and a plurality of inner alignment clips that are movable with respect to the plurality of outer preloading bars. The alignment clips are suspended from the preloading bars by flexible beam springs. A tub is etched in the microactuator substrate, and a first ferromagnetic keeper is plated on a bottom surface of the tub. A plurality of magnets are formed on the first ferromagnetic keeper in the tub. A flexure is formed with a second ferromagnetic keeper and a patterned conductor on an underside of the flexure below the second ferromagnetic keeper. The flexure is attached to the microactuator substrate with the patterned conductor positioned between the plurality of magnets and the second ferromagnetic keeper.